1. The Field of the Invention
The present invention concerns an optical fiber sensing device and in particular to such a device used to determine temperatures in a fired oil-treating device.
2. The Prior Art
It is well known that hydrocarbon products, when they initially are recovered from the ground, have a wide range of compositions and characteristics which require many different kinds of treatments. The preferred treatments for some of these hydrocarbon products is to initially heat the crude to approximately 210.degree. F. which causes separation of water and the volatile hydrocarbons from the remaining crude. This is generally accomplished by having a heater which sends flame into a closed burner conduit which traverses a portion of a tank substantially filled with the crude. The heat provided by this burner causes the previously mentioned separation. However, there is a danger that the heat provided by the burner may become too great causing the burner conduit to become exposed to the gas separated from the remaining crude. Unduly heating this gas, which is highly volatile, creates an extremely dangerous condition with the possibility of the gas being ignited by the hot burner conduit. In the past the solution for this problem has been to use thermocouples spaced along the burner conduit and adapted to actually control both the flow of fuel to the burner and flow of the crude into the tank to assure that the tank is always properly filled to the desired operating level. However, thermocouples have not always proved to be durable in this environment since the water separated from the crude is saline and therefore highly corrosive. Thus, the thermocouples must be provided with stainless steel wiring and the whole thing becomes rather clumsy and expensive.